In un-wounded skin, human keratinocytes (HKs) are destined to differentiate terminally into a mature Stratum corneum. When the skin is wounded, these same cells at the cut edge become highly migratory cells that do not differentiate and maintain the ability to divide. In non-healing wounds, however, HK migration is blocked and the wounds remain open subjecting patients to significant morbidity and sometimes fatality. The currently available treatments for chronic skin wounds show limited efficacy. However, these treatments are expensive as the national healthcare costs for delayed wound healing exceeds $9 billion per annum. Clearly, there is a pressing need for identifying novel and effective therapeutic targets to HK migration and to resume the wound re-epithelialization process in non-healing wounds. Biochemical fractionation of conditioned medium from migrating HKs allowed us to identify SECRETED heat shock protein-QOalpha (hspQOalpha) as a novel and essential promoter of HK migration. We demonstrated that: 1) Hsp90alpha is selectively secreted by migrating HKs, but not other types of human skin cells;2) TGFalpha rapidly stimulates hsp90alpha membrane translocation and secretion in HKs, but not in dermal fibroblasts (DFs);3) Comparison of human skin tissue staining and immunoblotting lysates of isolated human skin cells with anti-hsp90 antibodies suggests that extracellular hsp90alpha pre-exists in the epidermis of normal human skin;4) Recombinant hsp90alpha duplicates the pro-motility effect of TGFalpha or human serum on HKs;5) Neutralization of the extracellular hsp90alpha function completely blocks TGFalpha- or human serum-stimulated HK migration;6) Hsp90alpha does not affect HK proliferation;and 7) Most importantly, the topical application of recombinant hsp90alpha alone enhances skin wound healing in mice. In this proposal, we will further evaluate the therapeutic potential of secreted hsp90alpha in skin wound healing. Our research plans are: 1) to investigate the mechanisms of action by hsp90alpha that promotes HK migration in vitro;2) to understand how TGFalpha communicates with hsp90alpha;and 3) to take these findings to an in vivo human skin wound healing model. We suggest that extracellular hsp90alpha can replace human serum or growth factors to jumpstart the re-epithelialization process.